Fuel Economy - What do you get out of a tank? (3rd gens only)

[Boost King]

Just went for a drive to Moonta, 100km/hr most of the way, few 80 zones and some 60 zones getting out of surburbia. Average speed was 60km/hr per trip computer, scored a beauty of 8.6 l/100km. Even the wife was impressed as it regularly for city driving sits on 13l/100 with always soft driving.

Highway sure makes a difference. I saw at 110 k/hr it sat on 2,050 RPM in 4th (4 speed of course).

Car is a TJ Series 2 Advance 3.5ltr 4 speed.

Boosty

[shaness8]

Went up to the Murray and back averaged 8.4lt/100 pretty ordinary i reckon, my V8 commodore can match it on the same trip with twice the power.

[HaydenVRX]

Went up to the Murray and back averaged 8.4lt/100 pretty ordinary i reckon, my V8 commodore can match it on the same trip with twice the power.

Well the v8 should if its highway driving..

[shaness8]

Well the v8 should if its highway driving..

Why ?

[HaydenVRX]

Why ?

much more torque means less throttle is needed to keep the car going. + best fuel eco is closer to 100 in a v8 where in a v6 its closer to 80.

[Dave]

much more torque means less throttle is needed to keep the car going. + best fuel eco is closer to 100 in a v8 where in a v6 its closer to 80.

Hayden, i cant see the most economical speed for a commodore being 100. At these speeds, air resistance and rolling resistance play the most crucial part. The boxy commodore will have a v similar air resistance figure to the 380 so the most economical speed for the commodore will be around 80-90 too.

[shaness8]

Yeh they have more torque but that is because of the large capacity which needs more fuel to feed 6.0ltr, the most economical speed would be in the 60-80km range in most cars as their in top gear and pulling low revs with low wind resistance,

[mattgreen]

tj s2 vrx 5 speed auto. have just done over 2000kms in it (picked it up last thursday been driving it back from melb)
averaging at around 650km a tank on the highway
city and highway around 550km
mountains........ was around 15l per 100km wasnt driving it to rough
on the trip was averageing between 7l/100km to 12l/100km
so not to bad!
my manual 3L te did better tho redlined most its life and still gave me 450-500km to a tank. cant say it was babyed much....

[bb61266]

Why ?

Why V8?

A F1 Broadcaster years ago described the engine design problem - V8 - V10 V12 - it comes down to How bigger bang you can make (Cylinder size) vs how often you can make it (stroke & number of cylinders) - For formula 1 you wanted the "max" in power; - for fuel economy you want barely the least to turn over a high gear.

Now complicate this with the need to not run an engine too lean or it will burn up - and a V8 you would think would need more fuel with 2 more cylinders - but a v6 will "stall" out sooner than a v8 as it's "bang" ratio is lower and/or the bang is a bit bigger to compensate - so it's final drive ratio must be lower and/or uses more fuel to make the same ratio..

So a V8 with a really tall final gear will be able to make a lot of small bangs just keeping the car in motion which is what you want for hyper mile driving.

So a V12 would be better again in theory - but you need modern fuel management - not like my Jaguar Xj-S....